1) Prayer=wishful thinking. When one prays for results, they often put off their own responsibilities and hope that their "god" will take care of it for them. While you are praying for results, people are out there doing what is necessary to obtain those results. If people always simply prayed for results, we would never be able to find cures to disease and bad situations. Science is doing something about fixing the problems while you are simply praying for results to favor your cause. I always find it funny when a team prays for god to let them win because they deserve it. It is quite arrogant to assume that god should favor you over the other team. Instead of praying, try doing something about your problem.
2) I appreciate you praying for me, because it shows that you care. However, if you tell me that you're praying for me to "see the light" than I do not appreciate it. If you are going to pray for me, keep it to yourself. Once you tell me that you are praying for me, you come off as quite arrogant. It is as if you are saying that you know you're right and don't understand how I can't see that.
3) The effects of prayer are not observable in any way. For one to be able to conclude that a difference was made due to prayer, there would have to be a way to test this hypothesis. This is not possible to do without being able to observe the butterfly theory. One would have to engage in observing an exact situation with prayer and without it to see if any difference was made.
4) When someone says that they have seen prayer work in their life, they have no rational way to show it. If they pray to "god" for something, and they get it, than he answered their prayer. If they don't get what they asked for, than they say he still answered it, just not the way they wanted him to. With this logic, there is no way to make any sense of believing that any difference was made by praying. If everytime someone gets a disease, you pray for them to get better, there will be cases in which the person gets better. There will also be cases in which the person doesn't recover. Believers will attribute the cases that recovered to prayer, and the ones that didn't must have not been needed by god anymore. It must have been there time to go.
5) Example: If I believe that the "potato god" answers my prayers, I will as a result see things making me believe that this is true. When you believe something, your mind acts as a filter to make your beliefs seem true. This also causes closed-mindedness to alternatives. Let's say that I pray for my friend to not get in a car accident as he is driving under the influence. If he doesn't get in the wreck, than I will think that my prayer to the potato god must have protected him. If he does get in the wreck, than it must not have been the will of the potato god for him to not get in a wreck. This is highly irrational and flawed logic.
6)Any emotions attributed to prayer are a result of the placebo effect. I'm guessing you don't know about psychology, but you should research Albert Ellis. He explains how our beliefs lead to our actions which lead to our results which lead to our thoughts which lead back to our beliefs. It is a circle.
7) If anyone can make a "rational" argument for the power of prayer, by all means I am listening.
~Alan